The other day i adjusted my valve lash and while the valve cover was off i decided to re-torque my head bolts and they couldn't of been more than 90 ft/lb and that sort of scared me. did i just save myself from doing a head gasket

 

Those bolts are not torqued by numbers but by stretch (sort of the same thing ) the last turn is 90 deg ( think it is 90) from the where ever it landed at...so...you may have stretched a stretched bolt...

 

here's an answer
Torque to yield head bolts

Torque to yield (TTY) bolts, also commonly referred to as angle torque or stretch bolts, are used in many of today's modern engines predominantly for cylinder head bolts but also main bearing and big end caps.

Compared to conventional type bolts, TTY bolts offer the engine manufacturer a number of advantages including greater flexibility of design, reductions in component costs, more accurate assembly and reliability of seal. Engines designed utilising TTY head bolts require fewer head bolts to achieve the desired clamping loads then those using conventional bolts. With fewer bolts the engine manufacturer has more flexibility in cylinder head and block design as well as reducing the cost of the engine.

Whilst TTY bolts are attractive to the engine manufacturer, there are disadvantages to the engine repairer. For the most of us it would be unthinkable to replace a conventional head bolt unless the bolt was damaged, i.e. stripped threads, the bolt head was rounded off, the shank was severely corroded or pitted.

Conventional head bolts simply just did not wear out. Torque to yield head bolts however, by the very nature of their design, do wear out and should NEVER be reused.

 

Installing TTY Bolts

TTY head bolts are also tightened in a series of stages and in sequence, however they are not tightened to a predetermined torque, they are tightened through a series of specified angles. This data is provided by the engine manufacturer and should always be adhered to. While the first step in the tightening process is normally stated as a torque figure it is done so only to provide a uniform baseline from which the true load is then applied. This is commonly referred to as a pre-load or snug torque. A typical tightening specification would look as follows:

uniformly tighten in sequence in several passes to 78Nm

tighten in sequence 90°

tighten in sequence a further 90°

This procedure ensures that friction does not cause an uneven bolt loading and that the correct high tension is achieved every time during assembly. It is essential that a quality wrench with an accurate angle gauge be used to achieve the correct angles of turn of the tightening process.

Unlike a conventional bolt, TTY bolts are tightened beyond their elastic range past their yield point from which the bolt material can recover to its original length, and into the plastic phase of the bolt material. The bolt is permanently stretched and for this reason should not be reused. The reliability of these bolts once stretched is greatly reduced. If they are reused, they are permanently stretched further a second or third time. It is also for this reason why you should never retorque a torque to yield bolt.

Some engine manufactures provide a measurement within which a head bolt may be reused, however the age and history of the bolt is not taken into account. The bolt may well be within specification to pass a simple measurement test but the bolt could be very close to its shear point. Only one failed bolt can result in serious combustion leakage. The cost of a new set of TTY bolts is well justified when compared to the cost of having to repair an engine for the second time because of insufficient clamping load due to bolt fatigue.

 

so id be best off to install a new set of head bolts and on the other hand would it best to upgrade to studs or is that overkill for an engine that isnt making serious power.

 

To quote Corky Bell (loosely) Head bolts are a bean counter ans. to hold a head on.
Any engineer will tell you to use studs.....But in the long run if you are not bombing head bolts ought to do it for ya